Refurbishing old scientific and industrial equipment from eBay is something I love to do. If you understand what you’re looking for and are a savvy eBay user, you can score some amazing bargains on stuff that just a few years back was high-end, cutting edge, extremely expensive research-, factory-, and/or military-grade equipment. Garage quantum physicist (no, I’m not kidding) David Prutchi definitely has the knack, as witnessed, a couple weeks back, by his method for hacking a military surplus fallout probe into a general purpose, broad-spectrum high energy ionizing radiation detector.

This week, David has done it again with this excellent guide to building your own atomic clock from a used rubidium oscillator:

Efratom Model M-100 Rubidium Frequency Standard (RFS) oscillators are widely available in the surplus market. Units on eBay commonly sell in the $150 to $200 range. Despite their low surplus price, they were originally very expensive components, with superb performance. The M100 was designed to be used by the military as a master oscillator in high-performance communication systems, frequency standard equipment, advanced navigation equipment, and all other systems which require extremely precise frequencies and time intervals.

With the proper input power provided and suitable cooling provisions, you can turn a surplus M-100 into a free-standing 10 MHz +/-5×10-11 frequency standard for frequency counters, as well as a precise calibration source. I use mine to keep precise track of frequency when working on Earth-Moon-Earth (EME) communications, where even tiny errors in tuning can make the difference between success and failure to receive weak echoes.

I am descended from 5,000 generations of tool-using primates. Also, I went to college and stuff. I am a long-time contributor to MAKE magazine and makezine.com. My work has also appeared in ReadyMade, c’t – Magazin für Computertechnik, and The Wall Street Journal.